Supplement to Current Prospectus Initial Class & Service Class:

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1 MFS VARIABLE INSURANCE TRUST: MFS Core Equity Series MFS Global Equity Series MFS Growth Series MFS High Income Series MFS Investors Growth Stock Series MFS Investors Trust Series MFS Mid Cap Growth Series MFS New Discovery Series MFS Research Bond Series MFS Research International Series MFS Research Series MFS Strategic Income Series MFS Total Return Series MFS Utilities Series MFS Value Series Supplement to Current Prospectus Initial Class & Service Class: Effective immediately, under the main heading How to Purchase, Redeem, and Exchange Shares, the bulleted sub-items under the sub-heading entitled Other Considerations Frequent Trading up to, but not including Frequent Trading Risks, are replaced in their entirety by the following: Other Considerations Frequent Trading Right to Reject or Restrict Purchase and Exchange Orders. The fund is not intended to serve as a vehicle for frequent trading. The Board of Trustees of the fund has adopted the purchase and exchange limitation policies described below, which it believes are reasonably designed to discourage frequent fund share transactions. MFSC seeks to monitor and enforce these policies, subject to oversight by the Board of Trustees. The fund may alter its policies at any time without notice to shareholders. Purchase and Exchange Limitation Policies. The MFS funds reserve the right to restrict or reject, without any prior notice, any purchase or exchange order, including transactions believed to represent frequent trading activity. For example, MFSC may in its discretion restrict or reject a purchase or exchange order even if the transaction is not subject to specific exchange or other limitations described in this prospectus if MFSC determines that accepting the order could interfere with the efficient management of a fund's portfolio, increase costs to the fund, dilute the value of an investment in the fund to long-term shareholders, or otherwise not be in the fund's best interests. In the event that MFSC rejects an exchange request, neither the redemption nor the purchase side of the exchange will be processed. Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC's judgment, such delay would be in the fund s best interest, in which case both the redemption and purchase side of the exchange will receive the funds net asset values at the conclusion of the delay period. Financial Intermediary Purchase and Exchange Limitations. Financial intermediaries are required to reject any purchase or exchange orders in the fund if they believe the orders represent frequent trading activity unless they notify MFSC or an affiliate in writing that they do not monitor for frequent trading ( Waived Financial Intermediary ). With respect to Waived Financial Intermediaries, MFSC will take action reasonably designed to discourage frequent trading that is not in the best interests of the fund by the customers of such financial intermediary, including requesting underlying shareholder account data more frequently than from other financial intermediaries. Certain financial intermediaries may use procedures to restrict frequent trading by their customers who invest in the fund while others may not employ any procedures to restrict frequent trading. Such procedures, if any, may be less restrictive than the fund s purchase and exchange limitation policies, may permit transactions not permitted by the fund s purchase and exchange limitation policies, and/or may prohibit transactions not subject to the fund s purchase and exchange limitation policies

2 In addition, the terms of a particular insurance contract, plan or other eligible investment vehicle may also limit the ability of the insurance company, plan or other investor to prohibit transactions that MFSC might consider to be frequent trading. Please refer to your insurance company contract, plan or other material for the investment vehicle through which your investment in the fund is made regarding any restrictions on frequent trading. Limitations on the Ability to Detect and Curtail Frequent Trading Practices. There is no assurance that MFSC will be able to detect or prevent frequent trading. Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and MFSC is generally not able to identify trading by a particular underlying shareholder within an omnibus account, which makes it difficult or impossible to determine if a particular underlying shareholder is engaged in frequent trading. Omnibus accounts, in which shares are held in the name of a financial intermediary on behalf of multiple underlying shareholders, are a common form of holding shares among insurance companies offering insurance products and retirement plans. MFSC reviews trading activity to detect trading activity that may be indicative of frequent trading based on its internal parameters for detecting frequent trading, including reviewing transactions that exceed a certain dollar amount, transactions involving similar dollar amounts, or transactions that occur close in time to other transactions in the same account or in multiple accounts that are under common ownership or influence. Any or all of these parameters (including those not listed) may change at any time. If MFSC detects suspicious trading activity at the omnibus account level, it will contact the financial intermediary to request underlying shareholder level activity to determine whether there is underlying shareholder level frequent trading. However, the underlying shareholder data received may not reflect information about the ultimate underlying shareholders because there may be multiple layers of omnibus accounts. If frequent trading is identified, MFSC will take appropriate action, such as requesting the financial intermediary to prohibit purchases into the account by the underlying shareholder, requiring purchases by the underlying shareholder to be submitted only by mail, or prohibiting purchases from the financial intermediary. MFSC s ability to monitor and deter frequent trading in omnibus accounts depends on, among other factors, the frequency with which MFSC requests underlying shareholder account data from omnibus accounts. MFSC expects to request underlying shareholder data based on its assessment of the likelihood of frequent trading by underlying shareholders, among other factors. MFSC expects to request underlying shareholder data from Waived Financial Intermediaries more frequently than from other financial intermediaries. There is no assurance that MFSC will request data with sufficient frequency to detect or prevent frequent trading in omnibus accounts effectively. The date of this supplement is March 10,

3 VIT-VMM-LIQ-SUP-3/1/09 MFS VARIABLE INSURANCE TRUST: MFS Money Market Series Supplement to Current Prospectus: Effective immediately, the following is added to the Prospectus: The Board of Trustees that oversees the MFS Money Market Series (the Fund ), a series of the MFS Variable Insurance Trust (the Trust ), voted at its meeting held on February 24, 2009 to liquidate and terminate the Fund effective July 15, 2009, or as soon thereafter as practicable (the Termination Date ). As a result, the Fund is closed to new investments. Existing insurance company investors that currently offer the Fund as an investment option may continue to offer the Fund to their participants until the Termination Date. It is expected that the Fund will begin to liquidate portfolio securities in anticipation of its termination, and therefore may not be managed to meet its investment objective for a period of several days leading up to the Termination Date. The Fund will continue to declare a dividend daily to be paid at least monthly to shareholders who remain in the Fund through the Termination Date. Such shareholders will receive the cash equivalent of their proportionate interest in the Fund, including dividends that have been accrued, but not yet paid, on the Termination Date. Shareholders exempt from U.S. federal income taxation will not be liable for tax on any dividend or liquidating distribution. This Supplement also serves as formal notice of the Fund s termination pursuant to Section 9.2(a) of the Trust s Amended and Restated Declaration of Trust. The date of this Supplement is March 1,

4 MFS Money Market Series Initial Class Prospectus May 1, 2009 This prospectus describes the MFS Money Market Series. The fund's investment objective is to seek a high level of current income consistent with preservation of capital and liquidity. MFS Variable Insurance Trust The Securities and Exchange Commission has not approved or disapproved the fund s shares or determined whether this prospectus is accurate or complete. Anyone who tells you otherwise is committing a crime. 5/1/09 VMM-IPRO

5 Initial Class RISK RETURN SUMMARY... 1 EXPENSE SUMMARY... 4 MANAGEMENT OF THE FUND... 6 DESCRIPTION OF SHARE CLASSES... 8 HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES... 9 OTHER INFORMATION FINANCIAL HIGHLIGHTS... 13

6 RISK RETURN SUMMARY Investment Objective The fund s investment objective is to seek a high level of current income consistent with preservation of capital and liquidity. The fund s objective may be changed without shareholder approval. Principal Investment Strategies MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund s assets in money market instruments and repurchase agreements. MFS may invest the fund s assets in U.S. dollar-denominated foreign money market instruments. In buying and selling investments for the fund, MFS seeks to comply with industry-standard regulatory requirements for money market funds regarding credit quality, diversification and maturity. MFS stresses maintaining a stable $1 share price, liquidity, and income. In response to market, economic, political, or other conditions, MFS may depart from the fund s principal investment strategies by temporarily investing for defensive purposes. Principal Investment Types Money Market Instruments: Money market instruments are high-quality, short-term instruments that pay a fixed, variable, or floating interest rate. Money market instruments include bank certificates of deposit and other bank obligations, notes, commercial paper, asset-backed securities, U.S. and foreign government securities, and municipal instruments. U.S. Government Securities: U.S. Government securities are securities issued or guaranteed by the U.S. Treasury, by an agency or instrumentality of the U.S. Government, or by a U.S. Government-sponsored entity. Certain U.S. Government securities are not supported as to the payment of principal and interest by the full faith and credit of the U.S. Treasury or the ability to borrow from the U.S. Treasury. Some U.S. Government securities are supported as to the payment of principal and interest only by the credit of the entity issuing or guaranteeing the security. U.S. Government securities include mortgage-backed securities and other types of collateralized instruments issued or guaranteed by the U.S. Treasury, by an agency or instrumentality of the U.S. Government, or by a U.S. Government-sponsored entity. Repurchase Agreements: Repurchase agreements are agreements to buy a security from a third party at one price, with simultaneous agreements to sell it back to the third party at an agreed-upon price. Municipal Instruments: Municipal instruments are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, or financing for a specific project or public facility. Municipal instruments include general obligation bonds of municipalities, local or state governments, project or revenuespecific bonds, municipal lease obligations, and prerefunded or escrowed bonds. Municipal instruments may be fully or partially supported by the local government, by the credit of a private issuer, by the current or anticipated revenues from a specific project or assets, by the issuer s pledge to make annual appropriations for lease payments, or by domestic or foreign entities providing credit support, such as letters of credit, guarantees, or insurance. Principal Risks Although the fund seeks to preserve the value of your investment at $1.00 per share, you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. The principal risks of investing in the fund are: Interest Rate and Credit Risk: Although MFS seeks to maintain a stable $1.00 share price for the fund, there is no guarantee that it will be able to do so. A major or unexpected increase in interest rates or a decline in the credit quality of an issuer or entity providing credit support could cause the fund s share price to decrease to below $1.00. The value of a money market instrument can also decline in response to changes in the financial condition of the issuer or borrower, 1

7 changes in specific market, economic, industry, political, and regulatory conditions that affect a particular type of instrument, issuer, or borrower, and changes in general market, economic, political, and regulatory conditions. Foreign Exposure Risk: Exposure to foreign markets through issuers or entities providing credit support can involve increased risks. Political, social, and economic instability, the imposition of capital controls, or the expropriation or nationalization of assets in a particular country can affect the value of an investment. Bank Focus Risk: Events that affect the banking or related industries may have a significant adverse affect on the fund. Issuers in a single industry or related industries can react similarly to market, economic, political, or regulatory conditions and developments. Issuers in the banking industry are subject to many risks, including adverse government regulation, decreased availability and increased cost of capital, and changes in interest and/or default rates. Municipal Market Risk: The price of municipal instruments can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, and the financial developments of municipal issuers. Because many municipal instruments are issued to finance similar projects, especially those relating to education, health care, housing, utilities, and water and sewer, conditions in these industries can affect the overall municipal market. In addition, changes in the financial condition of an individual municipal insurer can affect the overall municipal market. Investment Selection Risk: The MFS analysis of an investment can be incorrect and its selection of investments can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. Counterparty and Third Party Risk: Transactions involving a counterparty other than the issuer of the instrument, or a third party responsible for servicing the instrument, are subject to the credit risk of the counterparty or third party, and to the counterparty s or third party s ability to perform in accordance with the terms of the transaction. Liquidity Risk: Certain investments and types of investments are subject to restrictions on resale, may trade in the overthe-counter market or in limited volume, or may not have an active trading market. As a result, it may not be possible to sell the investment at any particular time or at an acceptable price. Defensive Investing Risk: When MFS invests defensively, different factors could affect the fund s performance and the fund may not achieve its investment objective. In addition, the defensive strategy may not work as intended. Further Information Available Information about investment strategies and investment types not described in the Prospectus and the risks associated with those investment strategies and investment types are described in the fund s Statement of Additional Information ( SAI ). Bar Chart and Performance Table The bar chart and performance table below are intended to indicate some of the risks of investing in the fund by showing changes in the fund s performance over time. The chart and table provide past performance information. The fund s past performance does not necessarily indicate how the fund will perform in the future. The returns shown do not reflect fees and expenses imposed by the separate accounts established by insurance companies in order to serve as investment vehicles for variable annuity and variable life insurance contracts, qualified pension and retirement plans, and other eligible investors. If these fees and expenses were included, they would reduce the returns shown. Bar Chart. The bar chart shows changes over time in the annual total return of Initial Class shares for the past ten calendar years, and assumes the reinvestment of distributions. 2

8 10 Gain or Loss (%) % 5.93% 3.72% 1.31% 0.61% 0.78% 2.73% 4.62% 4.76% 1.86% Calendar Year The total return for the three-month period ended March 31, 2009 was 0.00%. During the periods shown in the bar chart, the highest quarterly return was 1.53% (for the calendar quarter ended September 30, 2000) and the lowest quarterly return was 0.08% (for the calendar quarter ended December 31, 2008). Performance Table. This table shows the average annual total returns of the fund and assumes the reinvestment of distributions. Average Annual Total Returns (for the periods ended December 31, 2008) Share Class 1 Year 5 Years 10 Years Initial Class 1.86% 2.94% 3.08% All performance results reflect any applicable fee and expense waivers in effect during the periods shown; without these, the results would have been lower. The fund commenced investment operations on January 3,

9 EXPENSE SUMMARY Expense Table This table describes the fees and expenses that you may pay when you hold shares of the fund. These expenses do not reflect the fees and expenses imposed by the separate accounts established by insurance companies in order to serve as investment vehicles for variable annuity and variable life insurance contracts, qualified pension and retirement plans, and other eligible investors, through which an investment in the fund is made. If these fees and expenses had been included, your expenses would be higher. The annual fund operating expenses below are based on expenses incurred during the fund s most recently completed fiscal year expressed as a percentage of the fund s average net assets during the period. The fund s annual operating expenses will likely vary from year to year. In general, a fund s annual operating expenses as a percentage of the fund s assets increase as the fund s assets decrease. Annual Fund Operating Expenses* (expenses that are deducted from fund assets): INITIAL CLASS Management Fee 0.50% Distribution and/or Service (12b-1) Fees. N/A Other Expenses (1) 2.84% Total Annual Fund Operating Expenses (1) % Fee Reductions (2). (2.74)% Net Expenses (1) % * MFS has voluntarily agreed to waive all or a portion of the management fee of the fund and bear some or all of the fund s expenses to avoid a negative yield for the fund. Such fee waiver is not reflected in the table. Had this fee waiver been taken into account, Total Annual Fund Operating Expenses" (and Net Expenses, if applicable) would be lower. MFS may terminate this voluntary waiver at any time. (1) The fund has entered into an expense offset arrangement that reduces the fund s custodian fee based upon the amount of cash maintained by the fund with its custodian. Such fee reduction is not reflected in the table. Had this fee reduction been taken into account,"net Expenses" would be lower. (2) MFS has agreed in writing to bear the fund s expenses such that "Other Expenses, determined without giving effect to the expense offset arrangements described above do not exceed 0.10% annually. This written agreement excludes management fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses, and will continue until at least April 30, Example of Expenses These examples are intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. These examples do not reflect the fees and expenses imposed by the investment vehicle through which an investment in the fund is made. If these fees and expenses were included, your expenses would be higher. The examples assume that: You invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); Your investment has a 5% return each year and dividends and other distributions are reinvested; and The fund s operating expenses remain the same, except that the fund s total operating expenses are assumed to be the fund s "Net Expenses" for the period during which any written fee reductions are in effect (see "Expense Summary - Expense Table" above). Although your actual costs will likely be higher or lower, under these assumptions your costs would be: 4

10 Share Class 1 Year 3 Years 5 Years 10 Years Initial Class $61 $770 $1,503 $3,444 5

11 MANAGEMENT OF THE FUND Investment Adviser Massachusetts Financial Services Company ( MFS ), located at 500 Boylston Street, Boston, Massachusetts, serves as the investment adviser for the fund. Subject to the supervision of the fund s Board of Trustees, MFS is responsible for managing the fund s investments, executing transactions and providing related administrative services and facilities under an Investment Advisory Agreement between the fund and MFS. For the fiscal year ended December 31, 2008, the fund paid MFS an effective management fee equal to 0.49% of the fund s average daily net assets. The management fee set forth in the Investment Advisory Agreement is 0.50% annually of the fund s average daily net assets. MFS may voluntarily agree to waive all or a portion of the management fee of the fund and agree to bear some or all of the fund s expenses for any reason, including to avoid a negative yield for the fund. MFS may terminate these voluntary waivers at any time. A discussion regarding the basis for the Board of Trustees approval of the Investment Advisory Agreement is available in the fund s most recent annual report for the one year period that ends December 31. MFS is America s oldest mutual fund organization. MFS and its predecessor organizations have a history of money management dating from 1924 and the founding of the first mutual fund, Massachusetts Investors Trust. Net assets under the management of the MFS organization were approximately $134 billion as of December 31, Disclosure of Portfolio Holdings. The MFS funds have established a policy with respect to the disclosure of fund portfolio holdings. A description of this policy is provided in the SAI. In addition, the following information is generally available to you on the MFS Web site (mfs.com) by clicking Products and Performance, then Variable Insurance Portfolios, then VIT, and then on a fund name: Information Approximate Date of Posting to Web Site Fund s top 10 securities holdings as of each month s end 14 days after month end Fund s full securities holdings as of each month s end 24 days after month end If a fund has substantial investments in both equity and debt instruments (e.g., a balanced fund), the fund s top 10 equity holdings and top 10 debt holdings will be made available. Note that the fund or MFS may suspend the posting of this information or modify the elements of this web posting policy without notice to shareholders. Once posted, the above information will generally remain available on the Web site until at least the date on which the fund files a Form N-CSR or Form N-Q for the period that includes the date as of which the Web site information is current. Administrator MFS provides the fund with certain financial, legal, and other administrative services under a Master Administrative Services Agreement between the fund and MFS. Under the Agreement, MFS is paid an annual fee for providing these services. Distributor MFS Fund Distributors, Inc. ( MFD ), a wholly owned subsidiary of MFS, is the distributor of shares of the fund. 6

12 Shareholder Servicing Agent MFS Service Center, Inc. ( MFSC ), a wholly owned subsidiary of MFS, provides dividend and distribution disbursing and transfer agent and recordkeeping functions in connection with the issuance, transfer, and redemption of each class of shares of the fund under a Shareholder Servicing Agent Agreement. MFSC receives a fee based on the costs it incurs in providing these services and a target profit margin. In addition, MFSC is reimbursed for out-of-pocket expenses. 7

13 DESCRIPTION OF SHARE CLASSES The fund offers Initial Class shares to separate accounts established by insurance companies to serve as investment vehicles for variable annuity and variable life insurance contracts, to qualified pension and retirement plans, and to any other person or plan permitted to hold shares of the trust pursuant to applicable Treasury Regulations without impairing the ability of insurance companies to satisfy the diversification requirements of Section 817(h) of the Internal Revenue Code (the "Code"). Financial Intermediary Compensation Insurance companies, plan sponsors, and other eligible investors to whom shares of the fund are offered (collectively, together with their affiliates, "Financial Intermediaries") receive various forms of compensation in connection with the sale of shares of the fund and/or the servicing of accounts. Financial Intermediaries may receive such compensation in the form of payments paid by MFD and/or one or more of its affiliates (for purposes of this section only, collectively, "MFD") from MFD s own additional resources. The types of payments described above are not exclusive and such payments can be significant to the Financial Intermediary. In addition, the compensation that Financial Intermediaries receive may vary by class of shares sold and among Financial Intermediaries. Depending upon the arrangements in place at any particular time, Financial Intermediaries may have a financial incentive to recommend a particular fund or share class. Financial Intermediaries may receive payments from MFD from MFD s own additional resources as incentives to market the MFS funds, to cooperate with MFD s promotional efforts and/or in recognition of their marketing, administrative services and/or processing support. This compensation from MFD is not reflected in the fees and expenses listed in the fee table section of the fund s prospectus. MFD compensates Financial Intermediaries based on criteria established by MFD from time to time that consider, among other factors, the level and/or type of marketing and administrative support provided by the Financial Intermediary, the level of assets attributable to and/or sales by the Financial Intermediary, and the quality of the overall relationship with the Financial Intermediary. You can find further details in the SAI about the payments made by MFD and the services provided by Financial Intermediaries. Financial Intermediaries may charge you additional fees and/or commissions other than those disclosed in this prospectus. You can ask your Financial Intermediary for information about any payments it receives from MFD and any services it provides, as well as about any fees and/or commissions it charges. Financial Intermediaries that market the funds may also act as, or be affiliated with, a broker/dealer in connection with a fund s purchase or sale of portfolio securities. However, the fund and MFS do not consider Financial Intermediaries' purchases of shares of the fund as a factor when choosing brokers/dealers to effect portfolio transactions for the fund. 8

14 HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES All purchases, redemptions, and exchanges of shares are made through insurance company separate accounts, qualified retirement and pension plans, and other eligible investors that are the record owner of the shares. Contract holders, plan beneficiaries, and other investors seeking to purchase, redeem, or exchange interests in the fund s shares should consult with the insurance company, plan sponsor or other eligible investor through which their investment in the fund is made. Insurance companies, plan sponsors, and other eligible investors are the designees of the trust for receipt of purchase, exchange, and redemption orders from contract holders and plan beneficiaries. An order submitted to the fund s designee by the valuation time will receive the net asset value next calculated, provided that the trust receives notice of the order generally by 11:00 a.m., Eastern time, on the next day on which the New York Stock Exchange is open for trading. The fund may reject for any reason any purchase orders. How to Exchange Shares An exchange involves the redemption of shares of one fund and the purchase of shares of another fund. You can exchange shares of your fund for shares of the same class of another fund at net asset value if shares of that fund are available for purchase by the insurance company separate account, plan, or other eligible investor through which your investment in the fund is made. See the prospectus or other materials for the investment vehicle through which your investment in the fund is made for a further discussion of the exchange privilege. You should read the prospectus of the fund into which you are exchanging and consider the differences in objectives, policies, and risks before making any exchange. Other Considerations Frequent Trading Right to Reject or Restrict Purchase and Exchange Orders. The Board of Trustees of the MFS funds has adopted the purchase and exchange limitation policies described below, which it believes are reasonably designed to discourage frequent fund share transactions. MFSC seeks to monitor and enforce these policies, subject to oversight by the Board of Trustees. The MFS funds may alter their policies at any time without notice to shareholders. Purchase and Exchange Limitation Policies. The MFS funds reserve the right to restrict or reject, without any prior notice, any purchase or exchange order, including transactions believed to represent frequent trading activity. For example, MFSC may in its discretion restrict or reject a purchase or exchange order even if the transaction is not subject to specific exchange or other limitations described in this prospectus if MFSC determines that accepting the order could interfere with the efficient management of a fund's portfolio, increase costs to the fund, dilute the value of an investment in the fund to long-term shareholders, or otherwise not be in the fund's best interests. In the event that MFSC rejects an exchange request, neither the redemption nor the purchase side of the exchange will be processed. Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC's judgment, such delay would be in the fund s best interest, in which case both the redemption and purchase side of the exchange will receive the fund s net asset value at the conclusion of the delay period. Financial Intermediary Purchase and Exchange Limitations. MFSC receives purchase, exchange and redemption orders through financial intermediaries. A financial intermediary s policy restricting frequent trading may be more or less restrictive than the MFS funds policies, may permit certain transactions not permitted by the MFS funds policies, or prohibit transactions not subject to the MFS funds policies. In addition, the terms of a particular insurance contract, plan or other eligible investment vehicle may also limit the ability of the insurance company, plan or other investor to prohibit transactions that MFSC might consider 9

15 to be frequent trading. Please refer to your insurance company contract, plan or other material for the investment vehicle through which your investment in the fund is made regarding the application of these limitations and any additional or different limitations. Omnibus Accounts. MFSC receives purchase, exchange, and redemption orders through certain financial intermediaries that hold omnibus accounts with an MFS fund. Omnibus account arrangements are common forms of holding shares of MFS funds, particularly among insurance companies offering insurance products and retirement plans. MFSC is generally not able to identify trading by a particular underlying shareholder within an omnibus account, which makes it difficult or impossible to determine if a particular underlying shareholder is engaged in frequent trading. For omnibus accounts for which MFSC does not regularly receive underlying shareholder data, MFSC reviews trading activity at the omnibus level to detect suspicious trading activity. This review is based on MFSC s internal parameters for detecting frequent trading, including reviewing transactions that exceed a certain dollar amount or transactions that occur close in time to other transactions in the same account or in multiple accounts that are under common ownership or influence. These parameters may change from time to time. If MFSC detects suspicious trading activity at the omnibus level it will contact the financial intermediary to request underlying shareholder level activity to determine whether there is underlying shareholder level frequent trading. If frequent trading is identified, MFSC will take appropriate action, such as prohibiting purchases into the account, requiring purchases by mail, or prohibiting purchases from the financial intermediary. Limitations on the Ability to Detect and Curtail Frequent Trading Practices. Depending upon the composition of a fund's shareholder accounts and the efforts made by certain shareholders to evade these limitations, MFSC may not be in a position to monitor and deter frequent trading with respect to a significant percentage of a fund's shareholders. MFSC s ability to monitor and deter frequent trading in omnibus accounts ultimately depends on the capability and cooperation of the financial intermediary and the frequency with which MFSC requests underlying shareholder account data from omnibus accounts. MFSC expects to request underlying shareholder account data less frequently from financial intermediaries who have adopted a policy restricting frequent trading that MFSC has determined is reasonably designed to identify and curtail trading activity that is not in the best interest of the funds than from other financial intermediaries. In certain instances, a financial intermediary may be unable to provide MFSC with information about underlying shareholder level activity. There is no assurance that MFSC will request data with sufficient frequency to detect or deter frequent trading in omnibus accounts effectively. Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and, despite the efforts of MFSC to prevent frequent trading, there is no assurance that MFSC will be able to identify such shareholders or curtail their trading practices. Frequent Trading Risks. To the extent that the MFS funds or their agents are unable to curtail excessive trading practices in a fund, these practices may interfere with the efficient management of the fund's portfolio, may result in increased transaction and administrative costs, and may adversely impact the fund s performance. Reservation of Other Rights. In addition to the rights expressly stated elsewhere in this prospectus, MFSC reserves the right to: 1) alter, add, or discontinue any conditions of purchase, service, or privilege at any time without notice; and 2) freeze any account or suspend account services when MFSC has received reasonable notice (written or otherwise) of a dispute between registered or beneficial account owners or when MFSC believes a fraudulent transaction may occur or has occurred. Anti-Money Laundering Restrictions. Federal law requires the fund to implement policies and procedures reasonably designed to prevent, detect and report money laundering and other illegal activity. The fund, consistent with applicable federal law, may redeem your shares and close your account; suspend, restrict or cancel purchase and redemption orders; 10

16 process redemption requests and withhold your proceeds; and take other action if it is unable to verify your identity within a reasonable time or conduct required due diligence on your account or as otherwise permitted by its anti-money laundering policies and procedures. Potential Conflicts. Shares of the fund are offered to the separate accounts of insurance companies that may be affiliated or unaffiliated with MFS and each other ( shared funding ) and may serve as the underlying investments for both variable annuity and variable life insurance contracts ( mixed funding ). Due to differences in tax treatment or other considerations, the interests of various contract owners might at some time be in conflict. The trust currently does not foresee any such conflict. Nevertheless, the Board of Trustees which oversees the funds intends to monitor events in order to identify any material irreconcilable conflicts which may possibly arise and to determine what action, if any, should be taken in response. If such a conflict were to occur, one or more separate accounts of the insurance companies might be required to withdraw its investments in the fund. This might force the fund to sell securities at disadvantageous prices. 11

17 OTHER INFORMATION Valuation The price of the fund s shares is based on its net asset value. The net asset value of the fund s shares is determined each day the New York Stock Exchange (the Exchange) is open for trading as of the close of regular trading on the Exchange (generally 4:00 p.m. Eastern time). However, net asset value may be calculated earlier in emergency situations or as otherwise permitted by the SEC. Net asset value per share is computed by dividing the net assets allocated to the fund by the number of shares outstanding for that fund. On days when the Exchange is closed (such as week-ends and holidays), net asset value is not calculated, and the fund does not transact purchase and redemption orders. To the extent the fund s assets are traded in other markets on days when the fund does not price its shares, the value of the fund s assets will likely change when you will not be able to purchase or redeem shares. To determine net asset value, the fund s investments are generally valued at amortized cost. Distributions The fund intends to declare a dividend daily and to pay these dividends to shareholders at least monthly. Any capital gains are distributed at least annually. Distribution Options Dividends and capital gain distributions will automatically be reinvested in additional shares of the fund. Tax Considerations The following discussion is very general. You are urged to consult your tax adviser regarding the effect that an investment in the fund may have on your particular tax situation, including possible foreign, state, and local taxes. The fund is treated as a separate corporation for federal income tax purposes. As long as the fund qualifies for treatment as a regulated investment company (which the fund has done in the past and intends to do in the future), it pays no federal income or excise taxes on the net earnings and net realized gains it timely distributes to shareholders. In addition, the fund intends to continue to diversify its assets to satisfy the federal tax diversification rules applicable to separate accounts that fund variable insurance and annuity contracts. Shares of the fund are offered to insurance company separate accounts, qualified retirement plans and pension plans, and other eligible investors. You should consult with the insurance company that issued your contract, plan sponsor, or other eligible investor through which your investment in the fund is made to understand the tax treatment of your investment. 12

18 FINANCIAL HIGHLIGHTS The financial highlights are intended to help you understand the fund s financial performance for the past five years (or, if shorter, the period of the fund s operation). Certain information reflects financial results for a single fund share. The total returns in the financial highlights represent the rate by which an investor would have earned (or lost) on an investment in the fund (assuming reinvestment of all distributions) held for the entire period. The returns shown do not reflect fees and expenses imposed by the investment vehiclethrough which an investment in the fund is made. If these fees and expenses were included, they would reduce returns. This information has been audited by the fund s independent registered public accounting firm, whose report, together with the fund s financial statements, are included in the fund s Annual Report to shareholders. The fund s Annual Report is available upon request by contacting MFSC (please see back cover for address and telephone number). The financial statements contained in the Annual Report are incorporated by reference into the SAI. The fund s independent registered public accounting firm is Deloitte & Touche LLP. Initial Class Years Ended 12/ Net asset value, beginning of period $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00 Income (loss) from investment operations Net investment income (d) $ 0.02 $ 0.05 $ 0.05 $ 0.03 $ 0.01 Net realized and unrealized gain (loss) on investments (0.00) (w) (0.00) (w) (0.00) (w) (0.00)(w) Total from investment operations $ 0.02 $ 0.05 $ 0.05 $ 0.03 $ 0.01 Less distributions declared to shareholders From net investment income $ (0.02) $ (0.05) $ (0.05) $ (0.03) $ (0.01) Net asset value, end of period $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00 Total return (%) (k)(r)(s) Ratios (%) (to average net assets) and Supplemental data: Expenses before expense reductions (f) Expenses after expense reductions (f) Net investment income Net assets at end of period (000 omitted) $ 2,166 $ 2,224 $ 2,127 $ 2,224 $ 2,804 (d) Per share data is based on average shares outstanding. (f) Ratios do not reflect reductions from fees paid indirectly, if applicable. (k) The total return does not reflect expenses that apply to separate accounts. Inclusion of these charges would reduce the total return figures for all periods shown. (r) Certain expenses have been reduced without which performance would have been lower. (s) From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower. (w) Per share amount was less than $

19 MFS Money Market Series Shareholder Communications with the Board of Trustees. The Board of Trustees of the MFS funds has adopted procedures by which shareholders may send communications to the Board. Shareholders may mail written communications to the Board to the attention of the Board of Trustees, [fund name], Massachusetts Financial Services Company, 500 Boylston Street, Boston, MA , Attention: Frank Tarantino, Independent Chief Compliance Officer of the Fund. Shareholder communications must (i) be in writing and be signed by the shareholder, (ii) identify the MFS fund to which they relate and (iii) identify the class and number of shares held by the shareholder. If you want more information about MFS Money Market Series, the following documents are available free upon request: Annual/Semiannual Reports. These reports contain information about the fund s actual investments. Annual reports discuss the effect of recent market conditions and investment strategies on the fund s performance during its last fiscal year. Statement of Additional Information (SAI). The SAI, dated May 1, 2009, provides more detailed information about the fund and is incorporated into this prospectus by reference. Because the fund is only available to insurance company separate accounts, qualified pension and retirement plans, and certain other eligible investors, the SAI and annual/semiannual reports for the fund are not available on mfs.com. You can get free copies of the annual/semiannual reports, the SAI and other information about the fund, and make inquiries about the fund, by contacting: MFS Service Center, Inc. P.O. Box Boston, MA Telephone: X3500 Information about the fund (including its prospectus, SAI and shareholder reports) can be reviewed and copied at the: Public Reference Room Securities and Exchange Commission 100 F Street, NE Washington, DC Information on the operation of the Public Reference Room may be obtained by calling the Commission at Reports and other information about the fund are available on the Edgar Database on the Commission s Internet Web site at / and copies of this information may be obtained, upon payment of a duplicating fee, by electronic request at the following address: publicinfo@sec.gov or by writing the Public Reference Section at the above address. The fund s Investment Company Act file number is